JPS61143115A - Method for cooling thermoplastic resin film - Google Patents

Abstract

PURPOSE:To uniformarize the temperature distribution of a cooled stretched film as far as possible thereby preventing it from sagging, by using a duct for discharging cooling air whose chamber is divided into a plurality of independent compartments. CONSTITUTION:Of ducts 2, each of four pairs of upper and lower ducts near an annealing treatment furnace 19 has a chamber that is divided into nine compartments, and cooling air is fed to these compartments or conduits 12 connecting these compartments and is blown through the compartments against a resin film 1. Other air is led to a duct whose chamber is not divided and is blown against the resin film 1. The temperature of the film in the cooling furnace is measured by an infrared thermometer 14, equi-distanced marking holes are formed in the film with the holes arranged in the direction of the width thereof, the distance between the holes is compared with the average value, and the amount of air discharged from the compartment corresponding to the particular position of the film is controlled, so that cooling of that part of the film is made equal to cooling of the other part of the film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for eliminating sagging in stretched films such as synthetic paper and cigarette packaging films.

[Prior art]

A polypropylene base film is longitudinally stretched at a temperature lower than the melting point of the polypropylene using the difference in circumferential speed between the rolls, and then propylene, which has a lower melting point than the polypropylene, is applied to the surface of the stretched base film. A molten film of ethylene copolymer or polyethylene is extruded into a laminate layer, and then the base layer is stretched in the transverse direction using a tenter at a temperature lower than the melting point of the polypropylene base material but higher than the insect point of the laminate resin. oriented and the laminate layer is non-oriented low temperature heat sealing film for cigarette boxes,
It is used as packaging film for candy boxes.

Further, a base film of polypropylene or polyethylene terephthalate containing inorganic fine powder is longitudinally stretched, then polypropylene or polyethylene terephthalate containing inorganic fine powder is extruded and melt-laminated on the surface of this longitudinally stretched film, and then the base resin is It is also known to manufacture synthetic paper in which both the base layer and the laminate layer are oriented by transversely stretching using a tenter at a temperature lower than the melting point of the laminating resin (Japanese Patent Publication No. 46-40794, No. 48
-8581).

Furthermore, polyethylene terephthalate, polyvinyl chloride,
Also known is an oriented film obtained by biaxially stretching a resin film such as a mixture of polypropylene and polyethylene containing fine inorganic powder (Japanese Patent Publication No. 31032/1983).

A stretched film having these orientations is usually heat-treated (annealed) by passing through an open chamber set at a temperature close to the melting point of the resin after completing transverse stretching using a tenter, and then guided into a cooling furnace. It is usually cooled with cooling air, then the ears are slit and then rolled up.

In the production of these stretched films, it is very difficult to maintain a uniform temperature inside the tenter-open furnace, so heaters at both left and right ends of the furnace are set higher than the central heater, and air is forced into the center of the film. Stretching is performed by attracting the material to make the temperature distribution uniform inside the opening.
The temperature cannot be the same on the left, right, and center sides of the furnace, and therefore, the degree of orientation differs depending on the part of the film, as shown in the heat shrinkage of the stretched film shown in Figure 3. The wound roll of the stretched film thus obtained has sag in the widthwise portion, portion, and winding diameter as shown in FIG. 2 under water, which is inconvenient for storage.

Furthermore, when cutting a stretched film such as a low-temperature heat-sealing film or synthetic paper into a sheet, problems may arise in dimensional accuracy.

The cause of the slack in the winding diameter of the stretched film is not only the non-uniformity of the temperature distribution inside the tenter open but also the non-uniformity of the temperature inside the cooling furnace. In particular, in the cooling furnace, the cooling efficiency at both ends of the film is lowered and the film temperature is high due to the gripping tool for the film which has passed through the stretching zone and the annealing zone and is heated. Therefore, the film has an uneven temperature distribution in the width direction. That is, as for non-uniformity in temperature distribution of a stretched film in a tenter oven, a cooling furnace, etc., even if cooling is performed under uniform cooling conditions in the width direction, non-uniformity in film temperature will naturally remain. Therefore, the portion of the stretched film with a high temperature of K11 is subject to pulling stress compared to the portion of the stretched film with a low temperature, and if the shrinkage stress of the film is large, this causes shrinkage and sag. On the other hand, if the take-off stress is greater than the film shrinkage stress, the film will elongate, but normally, increasing the take-off stress increases the residual stress in the wound film, which increases the sagging after opening, so this is preferable. do not have.

[Specific measures to solve the problem]

In the present invention, when cooling a stretched film that has been horizontally stretched by a tenter and subjected to an annealing treatment with cooling air, a duct is used in which the chamber of the duct for discharging cooling air is divided into a plurality of independent chambers, and the stretched film is The amount of cooling air discharged from the compartment corresponding to the high temperature part is increased so that the part of the stretched film can be cooled quickly, and the compartment corresponding to the low temperature part of the stretched film is Sagging is prevented by reducing the amount of cooling air discharged from the room so that the cooling of the stretched film is slowed down, and by making the temperature distribution of the cooled stretched film as uniform as possible. It is something.

The temperature distribution of this stretched film may vary depending on the temperature setting conditions and operating conditions of the tenter oven and annealing treatment furnace, so the positions of high temperature and low temperature areas may shift. Use.

That is, the present invention provides a cooling method for lowering the temperature of a thermoplastic resin film by blowing cooling air discharged from a plurality of ducts arranged above and below the resin film onto the front and back surfaces of the resin film. ) The plurality of ducts
Each duct is arranged in parallel in a direction perpendicular to the direction in which the resin film is sent out, and (3) the room of each duct is divided into a plurality of independent chambers, and (3) each of these divided Each of the divided chambers is connected to the divided chambers of the adjacent duct by a conduit, and the discharge amount of cooling air sent to the duct blades (D) and (B) is aligned in the direction in which the resin film is sent out. The present invention provides a method for cooling a thermoplastic resin film, which is characterized in that the thermoplastic resin film is discharged in a manner that the desired discharge amount is adjusted for each divided room in a row.

Examples of thermoplastic resins that can be used as film materials include polypropylene, polyamide, polyethylene terephthalate, polyethylene, polyvinyl chloride, and polystyrene. These resins may contain inorganic fine powders such as talc, fired clay, calcium carbonate, and titanium oxide, as well as heat stabilizers, lubricants, antistatic agents, ultraviolet absorbers, and the like.

Stretching is carried out in the longitudinal direction by 3 to 7 times using the peripheral speed difference between the roll groups, and in the transverse direction by 4 to 12 times using a tenter.

The stretching temperature is 15°C for polypropylene with a melting point of 164°C.
0-162°C is 108-125°C for polyethylene terephthalate, which has a melting point of 264°C.

Next, a cooling furnace used in the present invention will be explained using the drawings. Fig. 1 is a top view of the ducts (2, 2,...-) provided under the resin film (1) in the cooling furnace;
The figure is a front view of the cooling furnace, and FIG. 5 is a perspective view of the duct. In the figure, 3 is an outdoor air inlet, 4 is an indoor air inlet, 5 is a damper (moderation valve), 6 is a blower, 7 is a motor, and 8 is connected to the upper duct 2a, 2a... 9 is the main damper connected to the lower dampers 2b, 2b..., the sub-damper of the duct 2b1.2b2.2b3.2b4 in which the 1oaH room is divided, l
la, 11b, llc, lid, lie,
llf, l1g, lli are branch damper 2
Each club room AXB is divided into nine sections.

Damper that adjusts the discharge amount of cooling air of CSD, E, FXGSH, I, 12 is each duct 2b1.2b2.2b3
．． Club room divided into nine 2b4 rooms AXB, C.

・・・■ Adjacent club room (2br-A, 2b2-
A, 2b3-A, 2b4-A) (2bl-
B, 2b2-B, 2b3-B, 2b4-B
), ...... (2bt-I, 2M-I, 2bs-I
, 2b4-I) A conduit that connects the two, 13 is a manometer that reads the pressure of the cooling air discharged from the room, 10b is a duct 2bs in which the room is not divided,
2bs, 2b7.2b8 are sub-dampers that adjust the discharge amount of cooling air; 14 is an infrared thermometer movable in the width direction of the film; 15.15 is a film holder; 16 is an infrared thermometer that measures the temperature. Read, each damper 11a, llb
, . . . 111 is a converter for instructing the opening and closing of the damper, 17 is a VVVF inverter that receives information from the converter 16 and can convert the rotation speed of the motor 7, and 18 is a casing of the cooling furnace.

In Fig. 1, 19 is an annealing furnace for stretched resin films, 20 is a nozzle that blows cooling air onto the edges of the film, and the resin film is held from the annealing furnace side into the cooling furnace by rotating a chain. It is sent by the tool 15. In FIG. 1, a portion of the outlet of the cooling furnace is shown by a phantom line to help understand the width of the resin film.

An operating method for producing a resin film with little sagging using a small cooling furnace will be described below. The resin film 1 that has been horizontally stretched in the tenter oven is transferred to an annealing treatment furnace 1.
After being heat-treated at a temperature 5 to 10 degrees Celsius higher than the drawing temperature in 9 (sometimes it is designed to be integrated with a tenter oven furnace), it is sent to a cooling furnace and cooled to a temperature of about 20 to 60 degrees Celsius. Cooled by air.

Inside the casing 18 of the cooling furnace, eight pairs of ducts 2 are arranged vertically with a resin film 1 in between, and the ducts 2 are arranged at right angles to the flow direction of the resin film (direction of the arrow in Fig. 1).
The distance between each duct is 30-100m in parallel with a distance of 40cm.
Among these ducts 2, four pairs of upper and lower ducts 2b1.2b near the annealing processing furnace 19 are arranged at a distance.
2.2b3.2b4 has nine rooms A, B,...
Each duct (approximately 40 cm long) is connected to the adjacent chamber by a conduit 12, and each duct (2b1.2
b2.2b3.2b4) Same compartmentalized room symbol A
XA, A, A, B.

The amount of cooling air discharged from the chambers having BXB, B, . . . ■, ■, ■, ■ is approximately the same.

4 pairs of duns on the outlet side of the cooling furnace) 2b5.2b6.2b
7.2b8 is cooled so that the temperature distribution in the width direction of the resin film 1 is uniform in the four pairs of ducts 2b1.2b2.2b3.2b4, so the rooms of the latter four pairs of ducts are not divided. . Note that if the temperature distribution in the film width direction is not uniform in the former four pairs of ducts, the number of ducts having partitioned chambers is increased. Therefore, it may be possible to completely replace the duct with a duct having divided compartments.

The cooling air can be either outdoor air, indoor air, or both. In summer, the temperature inside the factory building is high, so it is better to draw air from outside through the suction port 3, and in winter, when the temperature of the outside air is too low, it is better to suck indoor air through the suction port 4. Of course, if the factory building is equipped with air conditioning equipment and the temperature inside the building can be kept constant, it is better to use indoor air.

The sucked air is sent to the upper duct 2 by the blower 6, passes through the main damper 8, and is sent to the lower duct 2 through the main damper 9 by a pipe. A portion of the air is guided to a nozzle 20' that cools the edges of the resin film 1 moving from the annealing furnace 19 to the cooling furnace.

The cooling air that has passed through the main damper 8.9 further passes through sub-dampers 10a and 10b, and one passes through branch dampers 11 & 111b...111 to reach the duct 2bx.

2b2.2bs, 2b4 divided club rooms A, B,・
... I or the conduit 12 connecting these chambers, and cooling air is blown onto the resin film 1 from each chamber. The other air is guided to a duct 2b5.2b6.2b7.2b8 in which the room is not divided, and is blown onto the resin film 1 from the discharge port.

The temperature of the resin film is set to 1, for example in an annealing furnace.
What was 60°C is cooled to 30-50°C at the outlet of the cooling furnace.

The amount of cooling air discharged from the ducts 2bl, 2bz, 2ba, and 2b4 is determined by moving the infrared thermometer 14 in the width direction of the film on a rail (not shown) and measuring the temperature of the film in the cooling furnace. On the other hand, before winding the film, as shown in Figure 6, after a certain period of time, mark marks (a, b, ... l) are placed on the film with a drafting needle at equal intervals in the width direction of the film. Drill a hole that passes through 3 to 4 sheets from the surface of the film, and set the distance between this mark in the film running direction m
lc...11 is read, and if the interval t between the marks is shorter than the average value, measures are taken to increase the amount of air discharged from the partitioned chamber of the duct corresponding to the film position. The opening of the branch damper (valve) is increased so that the cooling of that part of the film is equal to the cooling of other parts of the film. On the other hand, if the interval is longer than the average value, the opening degree of the corresponding branch damper valve should be adjusted to reduce the amount of air discharged from the divided room of the duct corresponding to the film position. Make it small so that the cooling of that part of the film is equal to the cooling of other parts of the film.

The amount of air discharged from each room is measured by manometer 13
It is understood by the air pressure recorded in

The distance t between the marks is such that long portions and short portions do not always appear at the same location in the width direction.

That is, the position of the air may shift due to a change in the amount of air discharged from each of the above-mentioned chambers, and the temperature distribution of the heated air within the tenter oven may change depending on the operating conditions.

Therefore, it is preferable to track this interval t at as short time intervals as possible, but always keep the film temperature distribution in the cooling furnace in the infrared rays so that the fluctuation of this t is within the smallest numerical range possible. It is preferable to read the discharge pressure of the cooling air from each chamber with an i-degree meter and a manometer at any time, and to operate so that the difference in temperature distribution of the film and the difference in discharge pressure are as small as possible.

The resin film, whose temperature distribution has become approximately uniform due to the air blown out from ducts 2bl and 2b2.2b3.2b4, can be further rolled up at room temperature to about 55°C by the air blown out from ducts 2b5.2b6.2b7.2bll. The material is cooled to a suitable temperature, then the ears are slit and rolled up.

(Effects) The resin film obtained by carrying out the present invention has small sag, and the winding diameter distribution in the width direction of the wound film is uniform, making it suitable for storage. Moreover, printing is also performed with high precision.

Reference example Mitsubishi Yuka@ polypropylene “Nopre 7MA-6” (
Product name) 90 parts, Mitsubishi Yuka ■ high-density polyethylene "Yukalonhar" EY-40 (Product name A) 100 parts, clay 15 parts, antioxidant 0.3 parts, and as a dispersant oleic acid manufactured by Kao Soap ■ A composition consisting of 0.1 part of "1 Lunatsuk" (trade name) was melted and kneaded using an extruder, then extruded into a sheet from a die at a temperature of 200°C, and the sheet was cooled to about 50°C. This sheet is then heated to about 150°C.
After heating to
Stretched twice.

Separately 1 polypropylene (Mitsubishi Noblen MA-6) 1
00 parts, 80 parts of clay with an average particle size of 1.5μ, an average particle size of 1
A composition containing 10 parts of μ titanium fluoride, 0.2 parts of an antioxidant, and 0.1 part of oleic acid was melt-kneaded using two other extruders, and heated to a temperature of 250°C from a die. laminated on both sides of the vertically stretched sheet in a sheet form,
Once cooled to a temperature 20℃ higher than room temperature, open the Raonate film with a tenter (the temperature distribution is 1
The film was heated to 75° C. (170° C. in the center) and reheated to about 155° C., stretched 8 times in the transverse direction using a tenter, and then passed through a heat treatment furnace at 160° C. for heat setting.

After cooling the edges of the heat-set stretched film with cooling air, the stretched film is introduced into a cooling furnace having eight pairs of ducts as shown in Fig. 1, and the discharge pressure of the cooling air from each duct is set to 40 W. The resin film was cooled to 45° C. with cooling air at the same temperature as Aq, and then the edges were slit, and 500 m of this stretched film was wound up.

This stretched film has a three-layer structure in which the thickness of the biaxially stretched film of the intermediate layer (base material layer) is 70μ, the thickness of the uniaxially stretched films of the front and back sides 1 is 10μ, and the horizontal Il @ 300 CrH. It was an excellent white stretched film.

The apparent density of this three-layer film is 0.78f/
In Cf, many fine voids were formed in both the base material layer and the front and back layers. In addition, many fine cracks were observed on the surfaces of the front and back layers.

When the winding diameter of this white stretched film was measured every 201M, the distribution was as shown in Table 1, and it is understood that there was sag.

The temperature distribution of the stretched film passing under each compartment of the duct and the length (l) of the markings attached to the stretched film at a given time in the flow direction are shown in Table 2.
It was as shown in

Stretched films having the winding diameter distribution shown in Table 1 were obtained in the same manner as in Reference Example, except that the discharge pressure of the cooling furnace was changed as shown in Table 2.

The temperature distribution of the stretched film during production and the length (t) of the markings attached to the stretched film were as shown in Table 2.

(Margin below)

[Brief explanation of the drawing]

FIG. 1 is a top view of a cooling furnace in which the present invention is implemented. Second
The figure is a perspective view showing a state in which a conventional stretched film is wound. Figure 3 shows the stretched film obtained in the reference example.
It is a figure which shows the heat shrinkage rate of the film feeding direction of the stretched film measured by leaving it to stand freely at 20 degreeC for 2 hours. FIG. 4 is a front view of the inside of the cooling furnace, and FIG. 5 is a perspective view of the upper part of the inside of the cooling furnace. FIG. 6 is a partial perspective view of the marked stretched film. In the figure, 1 is a film, 2 is a duct, A, B, C. D, E, F, G, H and ■ are divided chambers of the duct, 11Vi is a damper, and 12 is a conduit connecting the divided chambers.

Claims (1)

[Claims] 1) A cooling method in which cooling air discharged from a plurality of ducts arranged above and below the resin film is blown onto the front and back surfaces of the thermoplastic resin film to lower the temperature of the resin film. , (A) The plurality of ducts are (1) each duct arranged in parallel in a direction perpendicular to the direction in which the resin film is sent out, and (2) each duct has a plurality of independent chambers. (3) Each of the divided chambers is connected to the divided chambers of the adjacent duct by a conduit, and (B) the discharge amount of the cooling air sent to the duct is controlled by the valve. A method for cooling a thermoplastic resin film, characterized in that the resin film is discharged by adjusting the discharge amount to a desired discharge amount for each partitioned room in a row lined up in the direction in which the resin film is discharged. 2) The cooling method according to claim 1, wherein each duct is divided into nine compartments. 3) The cooling method according to claim 1, wherein four pairs of ducts are provided above and below the resin film. 4) The cooling method according to claim 1, wherein the amount of cooling air discharged from the divided chambers of the duct is controlled by opening and closing a valve based on reading the pressure of a manometer. 5) Claim 1, characterized in that the amount of cooling air discharged from each partitioned chamber of the duct increases from the central chamber of the duct toward the chambers at both left and right ends. cooling method. 6) The cooling method according to claim 1, wherein each duct is installed in a cooling furnace together with a resin film. 7) The cooling method according to claim 1 or 6, wherein the thermoplastic resin film is a stretched film. 8) The cooling method according to claim 7, wherein the cooling furnace is provided after the furnace for heat-treating the resin film laterally stretched by a tenter. 9) A patent claim characterized in that the temperature of the film passing through the final part of the divided duct in the cooling furnace is uniform in the center and both ends, or that both ends are 1 to 10 degrees Celsius lower than the center. The cooling method according to item 5 or 6.